U.S. Pat. No. 6,945,203 A1 discloses a two-stroke engine which operates with advanced scavenging. The piston of the two-stroke engine has a piston skirt to connect the air channel with the transfer channels. A small recess for reducing weight is provided above the piston skirt.
It is known to control the mixture inlet into the crankcase, the transfer windows and the outlet of the piston in two-stroke engines as they are for example used in hand-held work apparatus. In engines working with advanced scavenging the connection of the air inlet with the transfer windows is controlled via the piston skirt. Thus, many openings which at fixed predetermined times are to be connected to each other, to the combustion chamber, and/or to the crankcase open at the cylinder bore. For the implementation in a hand-held work apparatus, a two-stroke engine of this type must have a high power-to-weight ratio. High pre-compression of the mixture in the crankcase is desirable in order to achieve high power.